1. Field of the Invention
This invention relates to the field of monitoring the amount of an analyte, e. g., glucose, cholesterol, in body fluid. More particularly, this invention provides an article and method that monitors the amount of analyte in body fluid by means of a reagent that reacts with the analyte in the body fluid.
2. Discussion of the Art
The prevalence of diabetes has been increasing markedly in the world. At this time, diagnosed diabetics represented about 3% of the population of the United States. It is believed that the total actual number of diabetics in the United States is over 16,000,000. Diabetes can lead to numerous complications, such as, for example, retinopathy, nephropathy, and neuropathy.
The most important factor for reducing diabetes-associated complications is the maintenance of an appropriate level of glucose in the blood stream. The maintenance of the appropriate level of glucose in the blood stream may prevent and even reverse many of the effects of diabetes.
Glucose monitoring devices of the prior art have operated on the principle of first taking a sample of blood from an individual by any of a variety of methods, such as by needle or lancet. The individual then inserts a strip carrying reagents into a blood glucose meter in which glucose concentration is determined by a change in reflectance. The individual then applies the sample of blood to the strip. The blood reacts with the reagents and causes a change in reflectance of the strip, thereby indicating the concentration of glucose in the sample of blood. There are numerous devices currently available for diabetics to monitor the concentration of glucose in blood.
One of these devices is the "LIFESCAN" glucose meter. This glucose meter is sold under the tradenames "ONE TOUCH PROFILE" and "ONE TOUCH BASIC." This glucose meter and products associated therewith are described in U.S. Pat. Nos. 4,935,346; 5,304,468; 5,426,032; 5,563,042; 5,049,487; 5,059,394; 5,179,005, all of which are incorporated herein by reference. This glucose meter uses optical detection technology and a mixture of reagents comprising glucose oxidase, horse radish peroxidase, and color-generating materials known as chromogens. The reagents are located on "ONE TOUCH" reagent-carrying test strips. These devices suffer from the shortcoming of interference from serum components, which adversely affect the accuracy of glucose readings. The glucose oxidase reagent system suffers interference from such materials as bilirubin and ascorbic acid, both of which are always present in the blood in substantial amounts. Another shortcoming of these devices is that the blood applied to the "ONE TOUCH" test strip often migrates to the bottom surface of the "ONE TOUCH" test strip. The blood then transfers onto the glucose meter, and, as a result, users are required to clean the glucose meter after each use. Otherwise, residual blood remaining on the glucose meter will have a detrimental effect on the performance of the glucose meter or on the optical measuring component thereof.
In view of the aforementioned shortcomings, it would be desirable to provide a test strip having a reagent system that resists the effects of such blood components as bilirubin and ascorbic acid. It would also be desirable to provide a test strip that would minimize the migration of blood from the test strip to the glucose meter.